CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

315

A Quiescent NK Cell Phenotype With Gut Homing Potential in HIV-1 Exposed Seronegative Individuals kawthar Machmach Leggat 1 , Kombo F. N'guessan 1 , Isabella Swafford 2 , Leigh Anne Eller 2 , Shelly J. Krebs 2 , Merlin L. Robb 2 , Julie Ake 3 , Sandhya Vasan 1 , Dominic Paquin-Proulx 1 1 Henry M Jackson Foundation, Bethesda, MD, USA, 2 Henry M Jackson Foundation, Rockville, MD, USA, 3 Walter Reed Army Institute of Research, Silver Spring, MD, USA Background: HIV-exposed seronegative individuals (HESN) are a unique model to study mechanisms of protection against HIV-1. In previous studies, an increased NK cell activity has been correlated with protection in HESN, suggesting the involvement of the innate immune responses in decreasing the risk of HIV-1 acquisition. Here we compare circulating NK cell phenotype in HESN and HIV-exposed seroconverted (HESC) participants prior to HIV-1 acquisition. Methods: Specimens from participants in the RV217 Early Capture HIV Cohort (ECHO) were used to investigate NK cell in 25 HESC and 75 HESN participants. For our analysis, preinfection samples were collected for each HESC individual and were matched for collection time and location, age, gender, and risk behavior with 3 HESN. A 26-parameter flow cytometry panel was used to quantify NK cell frequency and phenotype. A pre-infection time point, between 28-365 days prior to first HIV positive test was chosen for the HESCs. Results: Compared with HESC individuals, NK cells from HESN participants were significantly less activated, as measured by the expression of HLA-DR (%, p=0.003 & MFI, p=0.001) and had a tendency for lower expression of the proliferation marker Ki67. Moreover, NK cells from HESN showed a higher potential to migrate to the gut measured by the expression of α4 β 7 (%, p=0.010 & MFI, p=0.015) and a lower expression of the inhibitory receptor ILT-2 (%, p=0.035 & MFI, p=0.023) compared to HESC participants. No differences were observed related to total NK cell frequency, distribution of the CD56hi immature, CD56dim mature, or CD56low NK cell subsets. No associations were found between NK cell phenotype and peak or set point viral load following acquisition in the HESC participants. Conclusion: Our preliminary data show significant differences in NK cells between HESN and HESC. The increased activation and expression of the inhibitory receptor ILT2, together with a lower expression of gut homing marker α4β7, suggest that NK cells from HESC participants might have an exhausted and dysfunctional phenotype with lower ability to migrate to the gut mucosa. It is possible that this may be associated with an increased risk of HIV-1 acquisition relative to a more beneficial quiescent NK cell profile as observed in the HESN participants. Mucosal-Homing Invariant NKT Cells Are Elevated in HIV-Exposed Seroconverters Prior to Infection Kombo F. N'guessan 1 , Kawthar Machmach Leggat 1 , Isabella Swafford 1 , Leigh Anne Eller 2 , Shelly J. Krebs 1 , Julie Ake 1 , Sandhya Vasan 2 , Merlin L. Robb 2 , Dominic Paquin-Proulx 1 , for the RV 217 Study Group 1 US Military HIV Research Program, Silver Spring, MD, USA, 2 Henry M Jackson Foundation, Bethesda, MD, USA Background: Studies in both humans and macaques have identified markers of HIV susceptibility such as the gut-homing integrin α 4β7, whose expression in memory CD4+ T cells increases in the context of HIV infection and is associated with increased susceptibility to acquisition. However, the phenotypic characteristics of unconventional T cells in the context of HIV

314

Exacerbation of the RSV Infectivity by SARS-CoV-2 in an In-Vitro Coinfection Cellular Model Claudia Vanetti , Silvia Zecchini, Gioia Cappelletti, Micaela Garziano, Irma Saulle, Sergio Strizzi, Fiona Limanaqi, Claudio Fenizia, Claudia Moscheni, Antonella Tosoni, Manuela Nebuloni, Mario Clerici, Daria Trabattoni, Mara Biasin University of Milan, Milan, Italy Background: Concurrent infections with two or more pathogens with an analogous tropism, such as Respiratory Syncytial Virus (RSV) and SARS-CoV-2, may antagonize or facilitate each other modulating host disease outcomes. Clinically, a severe phenotype has been reported in children with RSV/SARS-CoV 2 co- infections. However, experimental models to study the cellular, molecular and immunological dynamics of co-infections are extremely limited. Herein, we propose an in-vitro co-infection model to assess RSV/SARS-CoV-2 immune and viral evolution. Methods: A549-ACE2 expressing cells were single or co-infected with RSV and SARS-CoV-2 (MOI=0.01 each) (Figure 1A). SARS-CoV-2 and RSV replication was assessed at 24, 48 and 72 hours post infection (hpi) by Droplet Digital PCR (ddPCR), immune-fluorescent (IF) and transmission electron microscopy (TEM) analyses. Secretome analyses (17 Multiplex Cytokine ELISA) on cell culture supernatants and anti- viral/immune/autophagy gene expression (RT-qPCR) were evaluated as well. All the experiments were performed in the BSL3 facility. Results: The RSV/SARS-CoV-2 co-infection was characterized by a significant increase in the replication rate of RSV (co-infection vs single RSV p<0.001) (Figure 1B). The co-infection was able to modulate the viral host receptors' expression, as significant increase in ICAM1 expression, one of the RSV host receptors, was observed in the co-infected condition compared to the uninfected control (p<0.0001) and to the RSV (p<0.0001) and SARS-CoV-2 (p<0.0001) single infections. Remarkably, co-infection was accompanied by a significant rise in the expression of pro-inflammatory genes, further confirmed by secretome analysis. Moreover, substantial morphological changes were evident in the co-infected A549-ACE2 cells showing an increase in the number and length of cellular conduits. Finally, following co-infection, cells displayed a significant increase in LC3B gene expression (p<0.05), which was further confirmed by IF analysis, suggestive of an alteration of the autophagy pathway. Conclusion: The RSV/SARS-CoV-2 co-infection model displays a unique and specific viral and molecular fingerprint. These findings give clues of augmented severity upon RSV infection in the context of a concomitant SARS-CoV-2 co infection. This in-vitro co-infection model may represent an attractive, cost/ effective approach to mimic both viral dynamics and host immune responses, providing readily-measurable targets predictive of co- infection progression.

Poster Abstracts

316

66

CROI 2024